This invention relates to the detection of warm bodies and especially to detection apparatus combining a imaging device with an audio-monitored, far-infrared detection device.
A need exists in warfare, especially in guerrilla warfare in jungle terrain, for apparatus which can detect the presence of camouflaged opponents or enemies obscured by foliage. The detection of enemy soldiers is even more critical at night since this is when most guerrilla operations take place and since it is difficult to see soldiers at night even if they are not camouflaged or obscured by foliage.
Imaging devices are available for detection of humans under such conditions. There are scanning, far-infrared (far-IR) imagers; however these are expensive and are not easily portable because of their weight. There are visible light imagers, such as the so-called "starlight scope", and near-IR imagers. These are light in weight and relatively inexpensive. They depend on reflected natural background light or light from a near-IR searchlight. They provide an image of the surroundings but are not sensitive to the far-IR radiation emitted by objects near room temperature such as human bodies. Thus, they would not reveal a human being hidden in foliage, although they would detect him at night if he were in the open.
Another type of IR detection device is the so-called "Hansam", a single-channel, hand-scanned, audio-monitored far-IR detecting device. This is a passive device which detects heat (far-IR) emitted by a human body or other objects near room temperature. It is a small, light device which fits into a cylinder about the size of a searchlight and provides an audio, rather than a visual, signal. The operator of a Hansam may experience some difficulty when scanning the surroundings for warm objects in a night-time situation. Without an image to guide him, he may become disoriented and make scanning errors (miss large areas, aim too high, aim too low, etc.).